Pixel with transfer gate with no isolation edge

Abstract

A pixel and imager device, and method of forming the same, where the pixel has a transfer transistor gate associated with a photoconversion device and is isolated in a substrate by shallow trench isolation. The transfer transistor gate does not overlap the shallow trench isolation region.

1. An imager pixel, comprising:
 a substrate; 
 a photoconversion device comprising an active area in the substrate; and 
 a circuit configured to receive charge from the photoconversion device and output a signal representative of the charge, the circuit comprising a transfer transistor gate located over the substrate and entirely within the boundaries of the active area of the photoconversion device. 
 
     
     
       2. The imager pixel of  claim 1 , further comprising an oxide region surrounding the active area. 
     
     
       3. The imager pixel of  claim 2 , wherein said oxide region comprises a shallow trench isolation region. 
     
     
       4. The imager pixel of  claim 2 , further comprising at least one implant region in the active area of the photoconversion device between an edge of the transfer transistor gate and an edge of the oxide region. 
     
     
       5. The imager pixel of  claim 4 , wherein the at least one implant region comprises a p-type dopant. 
     
     
       6. The imager pixel of  claim 1 , wherein the circuit further comprises a reset transistor, a source follower transistor, and a row select transistor. 
     
     
       7. The imager pixel of  claim 1 , wherein at least a part of the circuit is shared with an adjacent pixel. 
     
     
       8. The imager pixel of  claim 1 , wherein an edge of the transfer transistor gate is angled across a corner of the photoconversion device. 
     
     
       9. A CMOS imager device, comprising:
 an active area in a substrate; 
 a photodiode in the active area; 
 a charge storage region in the active area; 
 a transfer gate located entirely within the boundaries of the active area, the transfer gate being configured to gate charge between the photodiode and the charge storage region; 
 a reset gate configured to reset the charge storage region; 
 a source follower gate configured to receive charge from the charge storage region; 
 a row select gate configured to couple the source follower gate to an output line; and 
 at least one implant region in the substrate adjacent an edge of the transfer gate. 
 
     
     
       10. The CMOS imager device of  claim 9 , further comprising an oxide region surrounding the active area. 
     
     
       11. The CMOS imager device of  claim 10 , wherein the at least one implant region is located between an edge of the transfer transistor and an edge of the oxide region. 
     
     
       12. The CMOS imager device of  claim 9 , wherein at least one of the reset gate, source follower gate, row select gate, and charge storage region is shared with an adjacent pixel. 
     
     
       13. The CMOS imager device of  claim 9 , wherein an edge of the transfer gate is angled across a corner of the photodiode. 
     
     
       14. A method of forming an imager pixel, comprising:
 providing an active area in a substrate; 
 forming a photoconversion device in the active area; 
 forming a transfer transistor gate entirely within the boundaries of the active area; and 
 forming at least one implant region adjacent an edge of the transfer transistor gate. 
 
     
     
       15. The method of  claim 14 , wherein an edge of the transfer transistor gate is formed across a corner of the photoconversion device. 
     
     
       16. The method of  claim 14 , further comprising the step of forming an oxide region surrounding the active area. 
     
     
       17. The method of  claim 16 , wherein the at least one implant region is formed between an edge of the transfer transistor and an edge of the oxide region. 
     
     
       18. The method of  claim 14 , wherein the step of forming an oxide region comprises forming a shallow trench isolation region. 
     
     
       19. The method of  claim 14 , further comprising the step of forming a reset transistor, a source follower transistor, and a row select transistor proximate the photoconversion device. 
     
     
       20. The method of  claim 19 , further comprising the step of forming a second photoconversion device that shares at least one of the reset transistor, source follower transistor, and row select transistor.